Prince Philip is continuing with his royal duties despite a prostate condition, the Standard can reveal today.

The 87-year-old has undertaken a series of official engagements since the condition was confirmed, probably in April after tests at the King Edward VII's hospital in London. The Duke of Edinburgh also has a heart condition.

But apart from a short period of rest at Windsor Castle, he has maintained a full schedule including a four-day tour of Turkey with the Queen, attending his eldest grandson Peter's wedding in Windsor, a tour of Scotland with the Queen and a three-day trip to Ghana.

When he was admitted to the £500-a-night hospital on 3 April, palace officials said it was a precaution after he developed a chest infection from a heavy cold. But medical sources say the trip was also used for checks on his prostate gland after routine tests days earlier showed high levels of PSA — a protein produced by the prostate and a warning sign for cancer.

Philip may have been kept in over the weekend because the procedure carries a small risk of infection. He is under the care of a leading urologist and the Queen's physician, Harley Street doctor Professor John Cunningham.

A policy of 'active surveillance' has been adopted, involving regular blood tests to check PSA levels are not rising. High future readings would indicate the tumour had become more aggressive and he would be given pelvis and chest X-rays and scans.

By the time men reach their eighties, more than half have cancerous cells on their prostate and tumours tend to develop slowly.

Philip was renowned for being impeccably fit into his sixties, passing a heart test to renew his pilot licence with nearly top marks when he was 63. He had a cancer scare in 1996 when he developed a growth on his nose. It was benign and he had it removed.

He has suffered from a heart condition for the past 15 years, for which he takes medication.

Tests last October revealed his circulatory system had weakened and it was feared his health had worsened in May when he developed a serious cough, potentially symptomatic of heart disease, during a visit to Turkey. He appeared to be gasping for breath but palace officials dismissed concerns.

Last weekend it emerged that Philip had given permission for his relatives to pre-record eulogies.

Today a royal source said: "Despite his heart problems and the condition, Philip's in robust health for a man of his age and is determined to plough on. He's always said he'll continue carrying out his royal duties until he's physically immobile and his role as the effective managing director of The Firm is not in question."

A Buckingham Palace spokesman said this morning: "There has been much speculation about Philip's health but we don't comment on the health of members of the royal family."

But this afternoon the palace issued a statement denying part of our report in an earlier edition.

It said: "The Duke of Edinburgh has authorised us to confirm that the claim made by the Evening Standard that he has received a 'diagnosis of prostate cancer' is untrue."